Emanuele ha già corretto l'italiano, io correggo solo l'inglese : )

Next Sunday I am going to Nagasaki with my friend to visit our friend from university.
My friend lives in Miyazaki. Miyazaki is south of where I live and Nagasaki is north of where I live, so he is picking me up and we are going together with his car.
It takes 4 or 5 hours from my house...very far.
The next day, Sunday, there is the Festival of Oysters in Nagasaki.
I want to eat many oysters^^
I'm really looking forward to our trip.

Have a wonderful visit with your friends, Chiaki!!  : )

Just a note about the future: 

When you have already made clear plans ahead of time and you know where and how you will do something, you should use the present continuous tense.  For example: "I am going to Nagasaki on Sunday." 

If you make a decision at that time, then you should use the future tense. For example if a friend calls you and asks you if you also want to go with him tomorrow... you can say "Yes, I will come too!".   This is a decision you made while you were talking, not something that was already planned when you talked with him.  

I'll give you a scenario:

Albert and Rachel:  Hello Lisa, would you like to come with us tomorrow?  We are going to the sea and then to a restaurant. 

Lisa:  Sure!  I will come too! 

Albert:  Ok, we will pick you up at 3.

Lisa:  Wonderful, see you tomorrow!  Thanks for inviting me!

Lisa to her friend Beatrice:   Hello Beatrice!  I am so happy! Tomorrow I am going to the sea with Albert and Rachel.  Then we are eating at a restaurant.  They are picking me up at 3.

Viaggio a Nagasaki

Il prossimo sabato andrò a Nagasaki con il un mio amico per vedere la una nostra amica.
Il mio amico vive a Miyazaki. Miyazaki è a sud di la mia casa di casa mia e Nagasaki è a nord di la mia casa di casa mia, così lui mi verrà a prendere e andremo insieme con la sua macchina.
Sono 4 o 5 ore da la mia casa da casa mia...è molto lontano.
Il prossimo giorno Il giorno dopo, domenica, c'è la festa dell'ostrica.
Voglio mangiare tante ostriche^^
Voglio andarci subito!

puoi dire "il prossimo sabato" oppure "sabato prossimo"